html export index

Dear all,

I have a problem at exporting my FrameMaker book to HTML5. I work with structured FrameMaker (Version 2015).

The export works well and the result is as expected. But only the table of content not. Either I can expand folders which are named like the files in the books. In there I can choose the chapters with level 2 headings. Or in some other cases I can expand the level 2 headings. In there I can choose the chapters with heading level 1 and 3.

I wonder, where FrameMaker gets the selection and structure of the index for the HTML export.

Thanks in advance for your help!

Matthias